In Long-Term Evolution (LTE) by the 3rd Generation Partnership Project (3GPP), the Radio Access Network (RAN) is totally optimized for packet-oriented applications with low latency and high-peak rates. In order to guarantee that the packets are correctly delivered to the upper layers, LTE employs a combination of ARQ (Automatic Repeat Request) and FEC (Forward Error Correction), also known as Hybrid-ARQ. In the uplink, the uplink control channel called the physical uplink control channel (PUCCH), in the format 1/1 a/1 b, is associated with the transmission of Hybrid-ARQ acknowledgements (Downlink ACK/NACKs for format 1a/1b) and scheduling requests (SRs for format 1). Within the PUCCH, multiple UEs can share the same time-frequency resources, the UEs being multiplexed via code division multiplexing (CDM) in the frequency domain and in the time domain, simultaneously.
A conventional receiver for PUCCH format 1/1 a/1b comprises a Matched Filter (MF) channel estimator, at time decorrelator and a frequency decorrelator followed by Maximal Ratio Combining (MRC). In such conventional PUCCH receiver, frequency decorrelation is performed first, time decorrelation is performed later and then MRC is finally performed, in order to retrieve all ACK/NACKs and/or SRs associated with each UE. That solution, although efficient, yields a large number of operations which are not always efficient in terms of performance of the decoder.